1. Field of the Invention
The invention relates to methods and instrumentation for use in preparing a bone surface for attachment of a prosthesis. More particularly, the invention relates to methods and instrumentation for aiding in the alignment and positioning of a resection guide relative to bone surfaces, in order to resect the bone surfaces and prepare them for attachment of endoprostheses. A common procedure in which this invention may be employed is knee arthroplasty.
2. Brief Description of the Prior Art
Joint replacement procedures, such as total knee arthroplasty, involve replacement of the load bearing surfaces of bones with artificial components. Proper implantation of these components, or implants, requires detailed measurements of the joint as well as accurate resections of the bone surfaces in preparation for their attachment to their respective components.
As used herein, when referring to bones or other body parts, the term “proximal” means closest to the heart, and the term “distal” means more distant from the heart. When referring to tools and instruments, the term “proximal” means closest to the practitioner, and the term “distal” means distant from the practitioner.
In attempting to duplicate the natural behavior of the joint, replacement components require specific positioning and attachment to the bones of the joint that they are to replace, in accordance with the detailed measurements. Commonly, since the bone-contacting surface of an implant, for example a distal femoral component, has a specific geometry, the bone to which it is to be attached must be accurately resected and shaped to mate with the geometry of the implant and provide the implant's proper alignment in the joint.
Measurement and placement of the distal femoral component, for example, requires determination of the following four orientations prior to implantation: proximal/distal, flexion/extension, varus/valgus, and internal/external rotation.
Various techniques and instruments are known for facilitating making these measurements and then resecting the bone surfaces accordingly. Examples of such are found in published U.S. patent application Ser. Nos. 20020133160, 20020133161, 20020133162 and 20020133163, as well as U.S. patent application Ser. No. 09/974,524, entitled “Methods and Tools for Femoral Resection in Knee Surgery”. These applications teach an alignment guide coupled to a bone anchor that is attached to the distal femur. The alignment guide is also joined to a resection guide via an attachment rod. Orientation and locking of the resection guide is done via three cam locks on the alignment guide. One cam lock is for adjusting and locking varus/valgus orientation, another is for flexion/extension, and a third is for proximal distal orientation of the resection guide relative to the distal femur. This alignment guide is therefore designed for independent locking of three orientation positions of the resection guide. Removal of the resection guide and attachment of further instruments would provide additional positioning capabilities.
Recently, various computerized systems have been introduced to aid the practitioner during different surgical procedures. These systems include multiple video cameras which are deployed above the surgical site and a plurality of dynamic reference frame (DRF) devices, also known as trackers, which are attached to body parts and surgical instruments. The trackers are generally LED devices which are visible to the cameras. Using software designed for a particular surgical procedure, a computer receiving input from the cameras guides the placement of surgical instruments.
Additionally, computer-assisted surgery has been developed which utilizes a tracking system that can relate positions on the patients and/or instruments to stored X-ray, CT scan and MRI data previously obtained for the patient. More recently, image free computer-aided surgery has been utilized where mechanical relationships can be calculated from anatomical reference points such as in joint arthroplasty. These systems are used intra-operatively for performing various surgical procedures, including replacement of artificial joints.
It has been especially useful to utilize trackable medical instruments for use in procedures utilizing computer-assisted image guided or image free medical and surgical navigation systems. Systems using body images are shown in U.S. Pat. Nos. 5,383,454 to Bucholz and 6,021,343 to Foley et al. In general, these image-guided systems use computer stored digital images of a body part obtained, for example, by CT scans taken before surgery, to generate images on a display, such as a CRT monitor screen, during surgery. These images are used in connection with real time information for representing the position of a surgical instrument with respect to the body part. The systems typically include tracking devices such as, for example, a tracker having LEDs and attachable to a surgical instrument as well as a patient's body part, a tracking array used in real time during surgery to track the position of the body part and the instrument via the tracker, and a monitor screen to display images representing the body and the position of the instrument relative to the stored images as the surgical procedure is performed.
An image-free type system is shown in U.S. Pat. No. 6,385,475. Some systems of this type include virtual joint images. In such systems, active or passive marker elements are attached to bones on opposite sides of a joint and a measuring device, such as an optical sensing camera coupled to a data processing system to which signals corresponding to the positioning data of the marker elements is supplied by the optical camera system, is used to correlate the markers on opposite sides of the joint. With a pointer mounted tracker, it is possible to locate various anatomic reference points on the joints to allow the system to position a cutting instrument such as a reamer or saw blade.
The prior art instrumnts used for determining the correct orientations for tibial and femoral resection in total knee arthroplasty, for example, leave room for optimization with respect to their designs, interaction with computer-assisted surgery instrumentation, as well as speed and ease of use.